That's what it looks like to me as well. Many games have the feature to set to either credit or extra ball. That doesn't make them an add-a-ball from my viewpoint. My Aztec is set to three ball extra ball.

I had a So76 and you could get chance to get an extra ball by knocking down all targets and this lights up center ball capture, but the Extra Ball capture light must be illuminated. The capture bonus has three options for Special, Extra Ball and Double Bonus. This is changed with one of the lane roll overs, lit star roll over or the drop target. If you get all of the rollover letters it lights the option for the Special. When you get rollovers and drops down the center capture rotates through all three.

On the So76 you could get an extra ball, double bonus and special with each and every ball. What they didn't do unfortuantely was reset the drops and rollovers. So once you got em all there isn't anything to shoot at until the ball drains to reset the table.

I don't know if New York is different but that was how the So76 was from memory. Gorgeous artwork from one of my favorites, Mr. Morison.